They look like normal pills, oblong and a little smaller than a daily vitamin.

But if your doctor writes a prescription for these pills in the not-too-distant future, you might hear a new twist on an old cliché: “Take two of these ingestible computers, and they will e-mail me in the morning.”

As society struggles with the privacy implications of wearable computers like Google Glass, scientists, researchers and some start-ups are already preparing the next, even more intrusive wave of computing: ingestible computers and minuscule sensors stuffed inside pills.

Although these tiny devices are not yet mainstream, some people on the cutting edge are already swallowing them to monitor a range of health data and wirelessly share this information with a doctor. And there are prototypes of tiny, ingestible devices that can do things like automatically open car doors or fill in passwords.

For people in extreme professions, like space travel, various versions of these pills have been used for some time. But in the next year, your family doctor — at least if he’s technologically adept — could also have them in his medicinal tool kit.

Inside these pills are tiny sensors and transmitters. You swallow them with water, or milk if you’d prefer. After that, the devices make their way to the stomach and stay intact as they travel through the intestinal tract.

“You will — voluntarily, I might add — take a pill, which you think of as a pill but is in fact a microscopic robot, which will monitor your systems” and wirelessly transmit what is happening, Eric E. Schmidt, the executive chairman of Google, said last fall at a company conference. “If it makes the difference between health and death, you’re going to want this thing.”

One of the pills, made by Proteus Digital Health, a small company in Redwood City, Calif., does not need a battery. Instead, the body is the power source. Just as a potato can power a light bulb, Proteus has added magnesium and copper on each side of its tiny sensor, which generates just enough electricity from stomach acids.

As a Proteus pill hits the bottom of the stomach, it sends information to a cellphone app through a patch worn on the body. The tiny computer can track medication-taking behaviors — “did Grandma take her pills today, and what time?” — and monitor how a patient’s body is responding to medicine. It also detects the person’s movements and rest patterns.